This exercise is great if you have sticking point mid to 3/4's up during the your bench press as due to the limited range of movement you cant build up mommentum which would normally help you drive through the sticking point during normally bench press. You start the pressing action basically at the sticking point making it much more difficult, but focusing on strength at the weak point in the movement.
To make the exercise more difficult after performing each rep, rest the weight at the bottom point for 4 - 6 seconds, this takes all of the tension of the muscles as your elbow rests on the floor. I was told this by one of the strength and conditioning coaches at the English instiute of sport that this length of time lets the elastic energy stored up from the eccentric contraction is lost. When the lift is started again its using the muscle recruitment from the concentric contraction only, rather then any advantage gained from the previous eccentric contraction. Kind of the opposite of plyometrics. This method can be useful for working past a sticking point but whether it as any other athletic benefits is yet to be shown, but suppose is a similar idea isometrics at a sticking point to produce as much tension as quickly as possible at a specific angle.